1. Dept. of Chemistry and Biochemistry Univ. of California Santa Barbara CA 93106 USA
2. Dept. of Physics Univ. of California Santa Barbara CA 93106 USA
3. Laboratory of Chemical Physics Nat. Institute of Diabetes and Digestive and Kidney Diseases, NIH Bethesda MD 20892-0520 USA
4. Dept. of Chemical Engineering Univ. of California Santa Barbara CA 93106 USA
5. Dept. of Chemistry Univ. of Durham Durham DH1 3LE UK
6. Dept. of Molecular, Cellular, and Developmental Biology Univ. of California Santa Barbara CA 93106 USA
7. School of Physics and Astronomy and the Biomedical Sciences Research Complex Univ. of St. Andrews St. Andrews KY16 9SS UK